Audi S3 Tail Light Bulb Size

The Audi S3 tail light utilizes 921 and 7440 bulb sizes for the specific lighting components located at the rear of the vehicle. Data for the bulb specifications covers the range from 2015 through 2020.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Inner Tail Light

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2023-2024	12961	12961	Check Price
2019	921	W16W	Check Price

Outer Tail Light

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2023-2024	1156	P21W	Check Price
2019	7506	7506	Check Price

Tail Light

Years	US Type	EU Type	Shop
2020	921	W16W	Check Price
2017-2019	7440	W21W	Check Price
2015-2016	921	W16W	Check Price

Bulb Specifications

Description	Type	Shop
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961	Check Price
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921	Check Price
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440	Check Price

Other Locations

Additional Notes

The 12961 is a Philips-designated miniature wedge bulb built to the T10 form factor with a W2.1x9.5d base, rated at 12V and 5W. It is the inner tail light bulb for the Audi S3 in 2023-2024.
The 921 is an ANSI-standard T15 wedge bulb rated at 12V and 16W. It serves as the inner tail light bulb on the S3 for the 2019 model year, and also appears in the unspecified sub-part rows for 2015-2016 and 2020.
P21W follows the ECE standard used in Europe and worldwide markets. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and is the outer tail light bulb for the S3 in 2023-2024.
The 7506 is the outer tail light bulb for the 2019 S3. The 7440 is an ANSI-standard single-filament T20 wedge bulb rated at 12V and 21W, appearing in the unspecified sub-part rows for 2017-2019.
The inner tail light position on the Audi S3 uses two distinct wattage levels across the listed years. The 12961 operates at 5W, while the 921 operates at 16W, meaning the two bulbs are not interchangeable despite both using wedge-style bases.
The outer tail light position similarly splits between wedge-base and bayonet-base designs. The P21W uses a BA15s bayonet fitting, while the 7506 and 7440 use wedge bases, making cross-year substitution physically incompatible without a socket adapter.
Both the P21W and the 7440 share a 21W rating and single-filament construction, but their base types differ. The P21W uses a BA15s bayonet base, and the 7440 uses a wedge base, so the shared wattage does not indicate interchangeability.